Northrop has GPS-aided stellar INS

Northrop Grumman delivered the first production LN-120G GPS-aided stellar-inertial navigation system to the U.S. Air Force last month, to begin the update of the service’s 31 RC-135 Rivet Joint signals intelligence aircraft.

For over three decades the RC-135 has used the mechanical gyro LN-120, but the new model greatly increases accuracy. As well as GPS updates, the LN-120G’s inertial systems can be updated by star-tracking. Once the system locates a star it refines the inertial system’s positional information, and by repeating this process it provides heading information accurate to 20 arc seconds, the highest accuracy currently available.

According to Mike Borck, Northrop Grumman’s stellar-inertial navigation program manager, “The LN-120G achieves positional accuracy of one-half of a nautical mile for up to 18 hours when GPS updating is unavailable or jammed.” Such accuracy is especially important to the RC-135, for which the positional accuracy of its gathered intelligence is only as good as that for the platform itself.

LN-120G was first flown in an RC-135 trials aircraft in August 2006. Borck said the LN-120G is also “ready to address the needs of aircraft like the B-52, B-2, Global Hawk or the new EP-8, which could benefit from its extremely precise navigation for intelligence, surveillance, reconnaissance and other applications.”